function isNumberKey(evt)
{
    var charCode = (evt.which) ? evt.which : event.keyCode
    if (charCode > 31 && (charCode < 48 || charCode > 57))
        return false;

    return true;
}

function cambiar (url) {

    document.images["imagen"].src = url;

}

function cambiar2 (url) {

    document.images["imagen2"].src = url;

}
